Fatigue Strength of Laser-processed Hot Work Tool Steel.

Hot work tool steel with an application in the die-casing industry was chosen as the test material. Most of the failure of dies depends on the heat check due to cyclic thermal stress. So, the present work aims to find a repair method of the failed tool. The microstructure of the Nd:YAG laser-processed material is formed by dendritic structure hardened into martensite. The steel shows secondary hardening by tempering and fatigue softening by cyclic loading even at room temperature. The rotating bending fatigue strength can be recovered to almost initial value by heat treatment at secondary hardening temperature after laser-processing. As the result, it is concluded that the laser processing is suitable for the repair of heat check.